Q. 45.0( 1 Vote )

A closed vessel is half filled with water. There is a hole near the top of the vessel and air is pumped out from this hole.
A. The water level will rise up in the vessel.

B. The pressure at the surface of the water will decrease.

C. The force by the water on the bottom of the vessel will decrease.

D. The density of the liquid will decrease.

Answer :

The water in the vessel is half down by gravity. To make it rise in the vessel, we need an additional force opposing the gravity. The pumping of air does not provide this force, hence option (A) is untrue.

As the air is pumped out, the number of air molecules decreases and hence the pressure decreases. Option(B) is therefore correct.


The force on the bottom of the vessel is due to the weight of the water and the pressure due to air. As it is pumped out, the total force on the bottom of the container decreases. This makes option (C) correct.


Changing air pressure does not affect the density of the liquid. Hence, option (D) is wrong.

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